Systems for upgrading petroleum-based compositions often experience plugging in the process lines from coke or other sludge material. Plugging refers to a stoppage or sharp decrease of flow in the process line, which may slow or stop the upgrading process. Additionally, if, due to the formation of coke and plugging material in the process line, the process flow stops or slows down, the delayed or stalled flow may further exacerbate the formation of plugging material.
Plugging material is not limited to coke. Highly viscous material can also cause plugging. Supercritical water reactor effluent, which may be a mixture of water, converted heavy oil, and unconverted heavy oil, is often in an emulsion state. The viscosity of the water-hydrocarbon emulsion decreases with high temperature. Thus, such emulsions may not cause any problems in a reactor operating at a high temperature. However, after leaving the reactor, the effluent is cooled down by a heat exchanger, which increases viscosity. This increased viscosity mixture may cause plugging in the process lines and may slow or interrupt the upgrading process.